1987 190 ac question.

[cici235]

I have a 1987 190d. It's been a great car with the exception of the ac system. After purchasing a rebuilt compressor that lasted about 3-4 months I spent big dollars on new compressor with a 3 year warranty. That was about a year ago. The ac is no longer cooling.

It may not be the compressor. I think it is more likely a climate control issue or other electrical problem. I am hoping someone on the forum can point me in the right direction.

I have not checked to see if voltage is being sent to the compressor. I will do this once someone answers my first question. The Low side switch is closed and shows full continuity. The high side switch located on the dryer shows to be completely open.

Should this be closed as well?

The car only has 97000 miles so I'm not quite ready to trade her in on a newer model quite yet.

[vstech]

do you know if there is refrigerant in it?
the open high side switch could be a defect, or it could be showing a loss of charge.
OVP and tach issues can hold out the a/c on these cars I believe.
I'm not an expert in the minutia of the mb a/c, just the refrigeration circuit itself...

[sixto]

The high side switch can remain open. It triggers the aux fan, nothing else.

Putting a condition on the forum to answer a question before you take an obvious step is like threatening yourself

Sixto
87 300D

[cici235]

It definably has refrigerant. If anything it could be a bit too much. With the car not running and a very hot 100 plus day the equalized pressure is just under a 130 psi. This was the firs thing I checked.

I added a portion of a can a few weeks ago. I don't remember what my gauges (they were in the acceptable range ) said but I do remember the car cooled much better. This is the first time since installing the compressor.

I did use a digital thermometer inserted in the vent while slowly adding the refrigerant. The bubbles in the sight tube for the most part cleared up and the temperature was always going the right direction. I think it ended up in the high 40's at idle. Not great but not sure what to expect for a car designed for r12. I think it gets colder when at higher speeds and after long periods of time.

Should I see what happens when I short the high side wires?

[cici235]

Originally Posted by sixto

The high side switch can remain open. It triggers the aux fan, nothing else.

Putting a condition on the forum to answer a question before you take an obvious step is like threatening yourself

Sixto
87 300D

Not really sure what you mean. I just submitted my last question before reading you response. You obviously answered my question.

thanks

If your inferring I should do more homework before asking questions. I apologize. I find the working on Auto Ac's like learning a foreign language. You forget just how little you once knew once you become proficient. So what is obvious to on may not be so obvious to another. I just assumed both were used to protect the compressor.

My next step will be to see if I am getting 12 volts to the compressor . My guess is I am not.

[sixto]

No, I got a chuckle out of the way you prefaced your question. It's like you'll hold your breath until someone answers your question

Jump the high pressure switch to engage the aux fan to see if that lowers vent temps.

Sixto
87 300D

[leathermang]

Originally Posted by cici235

It definably has refrigerant. If anything it could be a bit too much. With the car not running and a very hot 100 plus day the equalized pressure is just under a 130 psi. This was the firs thing I checked.

I added a portion of a can a few weeks ago. I don't remember what my gauges (they were in the acceptable range ) said but I do remember the car cooled much better. This is the first time since installing the compressor.

I did use a digital thermometer inserted in the vent while slowly adding the refrigerant. The bubbles in the sight tube for the most part cleared up and the temperature was always going the right direction. I think it ended up in the high 40's at idle. Not great but not sure what to expect for a car designed for r12. I think it gets colder when at higher speeds and after long periods of time.

Should I see what happens when I short the high side wires?

The FSM warns against using the sight gauge when filling the system due to the possibility of false ' add ' signals..
Particularly if a big blower is not directed into the condensor and the condensor and radiator both having clean and straightened fins...
Adding slowly and letting the system stabilize like 20 minutes per add of a couple of oz of refrigerant while checking the vent temps and pressures is much safer. The windows need to be down. ac on max, blower on LOW..... with fan on the condensor...
So with that resting pressure and your procedures and symptoms there is a good chance you have too much in the system.

[vstech]

... "not sure what to expect for a car designed for r12"
so... you have something OTHER than R12... what?
you filled to a bubble free condition with a replacement refrigerant? bad.

130 VP is a useless number aside from determining what type of refrigerant is in the car.
it will tell you NOTHING about the amount in the system. the pressure will be the same with 1/4 charge, and double charge...
you need airflow across the coil, you need system operating and you need refrigerant pressures and line temperatures to know if the system is charged.
find these things, and report back here, and we will assist you getting your a/c working to it's best ability.

[crs82]

Originally Posted by sixto

No, I got a chuckle out of the way you prefaced your question. It's like you'll hold your breath until someone answers your question

Jump the high pressure switch to engage the aux fan to see if that lowers vent temps.

Sixto
87 300D

This is exactly what I had to do to get cold air vent temps on my sisters 190E. Once that aux fan cam on, the temps dropped like a stone.

I jumped the switch, not held my breath.